<html>

<head>
<title>Learning WebGL &mdash; lesson 8</title>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">

<script type="text/javascript" src="glMatrix-0.9.5.min.js"></script>
<script type="text/javascript" src="webgl-utils.js"></script>

<script id="shader-fs" type="x-shader/x-fragment">
    precision mediump float;

    varying vec2 vTextureCoord;
    varying vec3 vLightWeighting;

    uniform float uAlpha;

    uniform sampler2D uSampler;

    void main(void) {
        vec4 textureColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
        gl_FragColor = vec4(textureColor.rgb * vLightWeighting, textureColor.a * uAlpha);
    }
</script>

<script id="shader-vs" type="x-shader/x-vertex">
    attribute vec3 aVertexPosition;
    attribute vec3 aVertexNormal;
    attribute vec2 aTextureCoord;

    uniform mat4 uMVMatrix;
    uniform mat4 uPMatrix;
    uniform mat3 uNMatrix;

    uniform vec3 uAmbientColor;

    uniform vec3 uLightingDirection;
    uniform vec3 uDirectionalColor;

    uniform bool uUseLighting;

    varying vec2 vTextureCoord;
    varying vec3 vLightWeighting;

    void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vTextureCoord = aTextureCoord;

        if (!uUseLighting) {
            vLightWeighting = vec3(1.0, 1.0, 1.0);
        } else {
            vec3 transformedNormal = uNMatrix * aVertexNormal;
            float directionalLightWeighting = max(dot(transformedNormal, uLightingDirection), 0.0);
            vLightWeighting = uAmbientColor + uDirectionalColor * directionalLightWeighting;
        }
    }
</script>


<script type="text/javascript">

    var gl;

    function initGL(canvas) {
        try {
            gl = canvas.getContext("experimental-webgl");
            gl.viewportWidth = canvas.width;
            gl.viewportHeight = canvas.height;
        } catch (e) {
        }
        if (!gl) {
            alert("Could not initialise WebGL, sorry :-(");
        }
    }


    function getShader(gl, id) {
        var shaderScript = document.getElementById(id);
        if (!shaderScript) {
            return null;
        }

        var str = "";
        var k = shaderScript.firstChild;
        while (k) {
            if (k.nodeType == 3) {
                str += k.textContent;
            }
            k = k.nextSibling;
        }

        var shader;
        if (shaderScript.type == "x-shader/x-fragment") {
            shader = gl.createShader(gl.FRAGMENT_SHADER);
        } else if (shaderScript.type == "x-shader/x-vertex") {
            shader = gl.createShader(gl.VERTEX_SHADER);
        } else {
            return null;
        }

        gl.shaderSource(shader, str);
        gl.compileShader(shader);

        if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            alert(gl.getShaderInfoLog(shader));
            return null;
        }

        return shader;
    }


    var shaderProgram;

    function initShaders() {
        var fragmentShader = getShader(gl, "shader-fs");
        var vertexShader = getShader(gl, "shader-vs");

        shaderProgram = gl.createProgram();
        gl.attachShader(shaderProgram, vertexShader);
        gl.attachShader(shaderProgram, fragmentShader);
        gl.linkProgram(shaderProgram);

        if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
            alert("Could not initialise shaders");
        }

        gl.useProgram(shaderProgram);

        shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
        gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);

        shaderProgram.vertexNormalAttribute = gl.getAttribLocation(shaderProgram, "aVertexNormal");
        gl.enableVertexAttribArray(shaderProgram.vertexNormalAttribute);

        shaderProgram.textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
        gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);

        shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
        shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
        shaderProgram.nMatrixUniform = gl.getUniformLocation(shaderProgram, "uNMatrix");
        shaderProgram.samplerUniform = gl.getUniformLocation(shaderProgram, "uSampler");
        shaderProgram.useLightingUniform = gl.getUniformLocation(shaderProgram, "uUseLighting");
        shaderProgram.ambientColorUniform = gl.getUniformLocation(shaderProgram, "uAmbientColor");
        shaderProgram.lightingDirectionUniform = gl.getUniformLocation(shaderProgram, "uLightingDirection");
        shaderProgram.directionalColorUniform = gl.getUniformLocation(shaderProgram, "uDirectionalColor");
        shaderProgram.alphaUniform = gl.getUniformLocation(shaderProgram, "uAlpha");
    }


    function handleLoadedTexture(texture) {
        gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);

        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texture.image);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);
        gl.generateMipmap(gl.TEXTURE_2D);

        gl.bindTexture(gl.TEXTURE_2D, null);
    }


    var glassTexture;

    function initTexture() {
        glassTexture = gl.createTexture();
        glassTexture.image = new Image();
        glassTexture.image.onload = function () {
            handleLoadedTexture(glassTexture)
        }

        glassTexture.image.src = "glass.gif";
    }


    var mvMatrix = mat4.create();
    var mvMatrixStack = [];
    var pMatrix = mat4.create();

    function mvPushMatrix() {
        var copy = mat4.create();
        mat4.set(mvMatrix, copy);
        mvMatrixStack.push(copy);
    }

    function mvPopMatrix() {
        if (mvMatrixStack.length == 0) {
            throw "Invalid popMatrix!";
        }
        mvMatrix = mvMatrixStack.pop();
    }


    function setMatrixUniforms() {
        gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
        gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);

        var normalMatrix = mat3.create();
        mat4.toInverseMat3(mvMatrix, normalMatrix);
        mat3.transpose(normalMatrix);
        gl.uniformMatrix3fv(shaderProgram.nMatrixUniform, false, normalMatrix);
    }


    function degToRad(degrees) {
        return degrees * Math.PI / 180;
    }



    var xRot = 0;
    var xSpeed = 3;

    var yRot = 0;
    var ySpeed = -3;

    var z = -5.0;


    var currentlyPressedKeys = {};

    function handleKeyDown(event) {
        currentlyPressedKeys[event.keyCode] = true;
    }


    function handleKeyUp(event) {
        currentlyPressedKeys[event.keyCode] = false;
    }


    function handleKeys() {
        if (currentlyPressedKeys[33]) {
            // Page Up
            z -= 0.05;
        }
        if (currentlyPressedKeys[34]) {
            // Page Down
            z += 0.05;
        }
        if (currentlyPressedKeys[37]) {
            // Left cursor key
            ySpeed -= 1;
        }
        if (currentlyPressedKeys[39]) {
            // Right cursor key
            ySpeed += 1;
        }
        if (currentlyPressedKeys[38]) {
            // Up cursor key
            xSpeed -= 1;
        }
        if (currentlyPressedKeys[40]) {
            // Down cursor key
            xSpeed += 1;
        }
    }


    var cubeVertexPositionBuffer;
    var cubeVertexNormalBuffer;
    var cubeVertexTextureCoordBuffer;
    var cubeVertexIndexBuffer;
    function initBuffers() {
        cubeVertexPositionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
        vertices = [
            // Front face
            -1.0, -1.0,  1.0,
             1.0, -1.0,  1.0,
             1.0,  1.0,  1.0,
            -1.0,  1.0,  1.0,

            // Back face
            -1.0, -1.0, -1.0,
            -1.0,  1.0, -1.0,
             1.0,  1.0, -1.0,
             1.0, -1.0, -1.0,

            // Top face
            -1.0,  1.0, -1.0,
            -1.0,  1.0,  1.0,
             1.0,  1.0,  1.0,
             1.0,  1.0, -1.0,

            // Bottom face
            -1.0, -1.0, -1.0,
             1.0, -1.0, -1.0,
             1.0, -1.0,  1.0,
            -1.0, -1.0,  1.0,

            // Right face
             1.0, -1.0, -1.0,
             1.0,  1.0, -1.0,
             1.0,  1.0,  1.0,
             1.0, -1.0,  1.0,

            // Left face
            -1.0, -1.0, -1.0,
            -1.0, -1.0,  1.0,
            -1.0,  1.0,  1.0,
            -1.0,  1.0, -1.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
        cubeVertexPositionBuffer.itemSize = 3;
        cubeVertexPositionBuffer.numItems = 24;

        cubeVertexNormalBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexNormalBuffer);
        var vertexNormals = [
            // Front face
             0.0,  0.0,  1.0,
             0.0,  0.0,  1.0,
             0.0,  0.0,  1.0,
             0.0,  0.0,  1.0,

            // Back face
             0.0,  0.0, -1.0,
             0.0,  0.0, -1.0,
             0.0,  0.0, -1.0,
             0.0,  0.0, -1.0,

            // Top face
             0.0,  1.0,  0.0,
             0.0,  1.0,  0.0,
             0.0,  1.0,  0.0,
             0.0,  1.0,  0.0,

            // Bottom face
             0.0, -1.0,  0.0,
             0.0, -1.0,  0.0,
             0.0, -1.0,  0.0,
             0.0, -1.0,  0.0,

            // Right face
             1.0,  0.0,  0.0,
             1.0,  0.0,  0.0,
             1.0,  0.0,  0.0,
             1.0,  0.0,  0.0,

            // Left face
            -1.0,  0.0,  0.0,
            -1.0,  0.0,  0.0,
            -1.0,  0.0,  0.0,
            -1.0,  0.0,  0.0
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertexNormals), gl.STATIC_DRAW);
        cubeVertexNormalBuffer.itemSize = 3;
        cubeVertexNormalBuffer.numItems = 24;

        cubeVertexTextureCoordBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
        var textureCoords = [
            // Front face
            0.0, 0.0,
            1.0, 0.0,
            1.0, 1.0,
            0.0, 1.0,

            // Back face
            1.0, 0.0,
            1.0, 1.0,
            0.0, 1.0,
            0.0, 0.0,

            // Top face
            0.0, 1.0,
            0.0, 0.0,
            1.0, 0.0,
            1.0, 1.0,

            // Bottom face
            1.0, 1.0,
            0.0, 1.0,
            0.0, 0.0,
            1.0, 0.0,

            // Right face
            1.0, 0.0,
            1.0, 1.0,
            0.0, 1.0,
            0.0, 0.0,

            // Left face
            0.0, 0.0,
            1.0, 0.0,
            1.0, 1.0,
            0.0, 1.0,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
        cubeVertexTextureCoordBuffer.itemSize = 2;
        cubeVertexTextureCoordBuffer.numItems = 24;

        cubeVertexIndexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
        var cubeVertexIndices = [
            0, 1, 2,      0, 2, 3,    // Front face
            4, 5, 6,      4, 6, 7,    // Back face
            8, 9, 10,     8, 10, 11,  // Top face
            12, 13, 14,   12, 14, 15, // Bottom face
            16, 17, 18,   16, 18, 19, // Right face
            20, 21, 22,   20, 22, 23  // Left face
        ];
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
        cubeVertexIndexBuffer.itemSize = 1;
        cubeVertexIndexBuffer.numItems = 36;
    }


    function drawScene() {
        gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
        gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

        mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);

        mat4.identity(mvMatrix);

        mat4.translate(mvMatrix, [0.0, 0.0, z]);

        mat4.rotate(mvMatrix, degToRad(xRot), [1, 0, 0]);
        mat4.rotate(mvMatrix, degToRad(yRot), [0, 1, 0]);

        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, cubeVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);

        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexNormalBuffer);
        gl.vertexAttribPointer(shaderProgram.vertexNormalAttribute, cubeVertexNormalBuffer.itemSize, gl.FLOAT, false, 0, 0);

        gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
        gl.vertexAttribPointer(shaderProgram.textureCoordAttribute, cubeVertexTextureCoordBuffer.itemSize, gl.FLOAT, false, 0, 0);

        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, glassTexture);
        gl.uniform1i(shaderProgram.samplerUniform, 0);

        var blending = document.getElementById("blending").checked;
        if (blending) {
            gl.blendFunc(gl.SRC_ALPHA, gl.ONE);
            gl.enable(gl.BLEND);
            gl.disable(gl.DEPTH_TEST);
            gl.uniform1f(shaderProgram.alphaUniform, parseFloat(document.getElementById("alpha").value));
        } else {
            gl.disable(gl.BLEND);
            gl.enable(gl.DEPTH_TEST);
        }

        var lighting = document.getElementById("lighting").checked;
        gl.uniform1i(shaderProgram.useLightingUniform, lighting);
        if (lighting) {
            gl.uniform3f(
                shaderProgram.ambientColorUniform,
                parseFloat(document.getElementById("ambientR").value),
                parseFloat(document.getElementById("ambientG").value),
                parseFloat(document.getElementById("ambientB").value)
            );

            var lightingDirection = [
                parseFloat(document.getElementById("lightDirectionX").value),
                parseFloat(document.getElementById("lightDirectionY").value),
                parseFloat(document.getElementById("lightDirectionZ").value)
            ];
            var adjustedLD = vec3.create();
            vec3.normalize(lightingDirection, adjustedLD);
            vec3.scale(adjustedLD, -1);
            gl.uniform3fv(shaderProgram.lightingDirectionUniform, adjustedLD);

            gl.uniform3f(
                shaderProgram.directionalColorUniform,
                parseFloat(document.getElementById("directionalR").value),
                parseFloat(document.getElementById("directionalG").value),
                parseFloat(document.getElementById("directionalB").value)
            );
        }

        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
        setMatrixUniforms();
        gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);
    }


    var lastTime = 0;

    function animate() {
        var timeNow = new Date().getTime();
        if (lastTime != 0) {
            var elapsed = timeNow - lastTime;

            xRot += (xSpeed * elapsed) / 1000.0;
            yRot += (ySpeed * elapsed) / 1000.0;
        }
        lastTime = timeNow;
    }


    function tick() {
        requestAnimFrame(tick);
        handleKeys();
        drawScene();
        animate();
    }



    function webGLStart() {
        var canvas = document.getElementById("lesson08-canvas");
        initGL(canvas);
        initShaders();
        initBuffers();
        initTexture();

        gl.clearColor(0.0, 0.0, 0.0, 1.0);
        gl.enable(gl.DEPTH_TEST);

        document.onkeydown = handleKeyDown;
        document.onkeyup = handleKeyUp;

        tick();
    }

</script>


</head>


<body onload="webGLStart();">
    <a href="http://learningwebgl.com/blog/?p=859">&lt;&lt; Back to Lesson 8</a><br />
    <canvas id="lesson08-canvas" style="border: none;" width="500" height="500"></canvas>

    <br />
    <input type="checkbox" id="blending" checked /> Use blending<br/>
    Alpha level <input type="text" id="alpha" value="0.5" /><br/>

    <br/>
    <input type="checkbox" id="lighting" checked /> Use lighting<br/>


    (Use cursor keys to spin the box and <code>Page Up</code>/<code>Page Down</code> to zoom out/in)



    <br/>
    <h2>Directional light:</h2>

    <table style="border: 0; padding: 10px;">
        <tr>
            <td><b>Direction:</b>
            <td>X: <input type="text" id="lightDirectionX" value="-0.25" />
            <td>Y: <input type="text" id="lightDirectionY" value="-0.25" />
            <td>Z: <input type="text" id="lightDirectionZ" value="-1.0" />
        </tr>
        <tr>
            <td><b>Colour:</b>
            <td>R: <input type="text" id="directionalR" value="0.8" />
            <td>G: <input type="text" id="directionalG" value="0.8" />
            <td>B: <input type="text" id="directionalB" value="0.8" />
        </tr>
    </table>

    <h2>Ambient light:</h2>

    <table style="border: 0; padding: 10px;">
        <tr>
            <td><b>Colour:</b>
            <td>R: <input type="text" id="ambientR" value="0.2" />
            <td>G: <input type="text" id="ambientG" value="0.2" />
            <td>B: <input type="text" id="ambientB" value="0.2" />
        </tr>
    </table>

    <a href="http://learningwebgl.com/blog/?p=859">&lt;&lt; Back to Lesson 8</a>
</body>

</html>
